SURFACTANT INTERACTIONS 273 shorter-chain surfactants in cleaning the insoluble SAC:detergent complexes left on hair by the use of conventional detergents. This was tested by performing light-scattering measurements on tresses that were washed twice with SODS or TEALS following deposition of a TEALS/SAC complex on the surface. In Table V, it is seen that attempting to remove the TEALS/SAC complex with TEALS did not result in significant cleaning, leaving tresses that were still sub- stantially dulled. The SODS treatment, on the other hand, restored most of the original shine, indicating that the complex was effectively cleaned. We conclude, therefore, that detergents such as SODS are superior cleaners, not only of conditioner, but of the insoluble conditioner:detergent complexes left on hair as a result of washing with conventional detergents. Half-head tests. In addition to tests on single fibers and on tresses, light-scattering results can be obtained from experiments on actual heads of hair. In order to test detergent/conditioner interactions under conditions as close as possible to actual con- sumer use, therefore, a series of half-head tests was run in which SAC/TEALS and SAC/SODS treatments were compared. Table VI lists the results of these treatments on ten panelists. A plus sign in the column labeled subjective shine means the SODS-washed side was judged shinier by the eval- uators, while a positive value in the delta shine column indicates that the SODS-treated side had the larger measured shine value. In all ten cases, the SAC/SODS-treated half of the head was found to have the greater measured shine value, while in only one case was the SAC/TEALS-treated side judged to have the greater subjective shine. Application of a simple sign test to these results indicates a difference between the TEALS- and SODS-treated sides at a greater than 99% level of confidence. This confirms that the dulling effects arising from formation of insoluble complexes can be easily observed under conditions similar to actual consumer use. The one discrepancy above, between instrumental and subjective evaluations, is prob- ably an orientation effect. Shine is observed when an object scatters much more light in a particular direction than in other directions (1). Thus, even if individual hairs in an array are very shiny, the less parallel they are to each other the less they will reflect light in the same direction, resulting in a decrease in perceived shine. The hair in half-head test 6 was quite curly, so it is reasonable to assume it would be more sensitive to orientation effects of this type. Note that the largest differences in measured shine were observed with permed or Table V SAC/TEALS Complex Experiments • Treatment Shine 2 SODS 1.72 (0.23) Complex (SAC/TEALS) 0.67 (0.12) Complex/TEALS 0.87 (0.11) Complex/SODS 1.43 (0.23) Shine values connected by a vertical line were not significantly different. Numbers in parentheses are standard deviations.

274 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table VI SAC Half-Head Tests. (SODS vs TEALS) Test no. Subjective • shine Delta 2 shine 13 q- 0.26 2 + 0.12 3 + 0.11 4 + 0.38 5 + 0.50 6 - 0.44 74 q- 0.80 85 + 0.38 9 + O.63 104 q- 0.80 • A positive sign means SODS-treated side judged shinier. 2 This is the difference between shine values measured for SODS and TEALS-treated sides. A positive value means SODS side had greater shine. 3 Tests 1-3 were performed on the same woman. 4 These women had permed hair. 5 Tests 8 and 9 were performed on same woman before and after application of a hair-straightening treatment. straightened hair. This is not surprising since chemically treated hair has a greater number of negative charges on the surface and would be expected to bind more cationic conditioner. This is confirmed by the observation from radiotracer experiments that permed hair binds 2.3 times more SAC than virgin hair (6). Cleaning of commercial conditioners. The preceding experiments dealt for the most part with SAC, a conditioner active found in many commercial products. Experiments were also performed with conditioner A, a commercial conditioner containing SAC and ceteth-2, in order to determine whether the results reported for SAC would also be observed with commercial products. Tresses treated with conditioner A and then washed with TEALS were found to exhibit much less dulling than was observed when washing SAC-treated tresses. This is prob- ably the result of solubilization of the SAC by the ceteth-2 oil. In order to increase the sensitivity of the experiments, therefore, measurements were made using permed tresses which, as was noted in the preceding section, adsorb more conditioner than does virgin hair. Table VII tabulates the light-scattering results from a typical permed hair experiment. In this case it is seen that, as was observed for SAC-treated hair, washing conditioner A-treated hair with TEALS resulted in duller tresses than those washed with the shorter- chain surfactants comprising SODS. This was confirmed by panelists who subjectively evaluated tresses according to the methods described in reference 1. These results indicate that, although the dulling effect is smaller, formation of insoluble complexes between TEALS and SAC still occurs with commercial conditioners. Note that the shine values in Table VII were obtained at 45 ø incidence and thus cannot be compared directly with the 30 ø incidence shine values listed in the previous tables. The reason for this is that specular reflection increases with increasing angle of incidence (Fresnel's equations, reference 3).